How much do asthmatics breathe?
In 1968 The New England Journal of Medicine published the results of a large study in which breathing and blood gases of a group of asthmatics were investigated. The researchers found that all 101 tested patients had chronic alveolar hyperventilation. Those asthmatics who had a light or moderate degree of the disease breathed about 15 l of air per min or 2.5 times more than the official medical norm (6 l/min).
More recently, in 1995, American researchers from the Mayo Clinic and Foundation (Rochester) confirmed the same average value (about 15 l/min) for another group of patients diagnosed with asthma (Johnson et al, 1995). This study was published in the Journal of Applied Physiology.
Finally, medical professionals from Mater Hospital in Brisbane (Australia) tested 39 asthmatics and found 14 l/min (Bowler et al, 1998), as it was reported in the Medical Journal of Australia.
What evidence exists that low CO2 levels will cause problems with air passages?
Clinical Science published an article in 1968 titled "The mechanism of bronchoconstriction due to hypocapnia in man" (“hypocapnia” means abnormally low CO2 concentrations). In the artcile, Sterling explained that CO2 deficiency causes an excited state of the cholinergic nerve. Since this nerve is responsible for the state of the smooth muscles in bronchi, its excited state leads to the constriction of air passages.
What about modern textbooks on physiology? One states, “Agents that tend to dilate airways include increased PaCO2 (hypoventilation or inspired CO2),” (p.545, R. Berne & M. Levy, 1998). This textbook directly claims that slowing down breathing (hypoventilation) or increased CO2 level dilates airways. Moreover, CO2 is suggested as the chief chemical substance that promotes this effect.
What about the asthma-ventilation connection? Professor Buteyko proposed this link in the 1950’s (his first official publication was published probably by 1964) when he discovered the central role of overbreathing in the development and degree of asthma. (He and his colleagues also found that asthma patients got immediate relief from their asthma attack symptoms, if they practiced reduced breathing).
Dr. Herxheimer independently suggested that low CO2 was the cause of bronchial asthma in 1946 and 1952 (Herxheimer, 1946; 1952).
How do asthma and asthma attacks develop?
Let us consider the possible mechanism suggested by Professor Buteyko. Low CO2 values in the bronchi cause chronic constriction of airways (that happens in all people). In addition to this direct effect, chronic hyperventilation makes immune reactions abnormal. The immune system becomes too sensitive in relation to intruders from outside (coming with air or food), but weakens the responses to various pathogens, like viruses and bacteria. (That makes sense since hyperventilation is a defensive reaction and a part of the fight-or-flight response. Hyperventilation then should mean a state of increased alertness and emergency for the whole organism, the immune system included.)
The immune system becomes hypersensitive and seemingly innocent events like breathing cold air or inhaling dust particles can trigger an inflammatory response in asthmatics, excessive production of mucus, a sense of anxiety or panic, more hyperventilation, and further constrictions of airways.
As a result, mucus makes air passages narrower (or even blocks some of them) creating a feeling of suffocation and causing asthma attacks. During an attack, an asthmatic may try to clear the mucus by coughing it out, but that further reduces CO2 concentrations in the lungs and makes air passages narrower.
For the list of the quoted references click here
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